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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2007

Unveiling the X-ray/TeV engine in Mkn 421

B. Giebels
  • Fonction : Auteur
G. Dubus
B. Khélifi

Résumé

Aims.Our goal was to find important clues concerning particle acceleration in relativistic jets through the analysis of multi-wavelength observations of TeV blazars. Methods: Simultaneous observations of Mkn 421 were taken in very high energy γ-rays (>200 GeV, CAT experiment), X-rays (RXTE), and optical (KVA). Multi-day RXTE observations are also presented, allowing for detailed modelling of the spectral variability. Results: Short timescale (≈30 mn) variations in VHE γ-rays are found, correlated with X-rays, but not with the optical. The X-ray spectrum hardens with flux until the photon indices saturate above a threshold flux ≈10-9erg s-1 cm-2. The fractional variability decreases from X-rays to optical as a power law with F_var∝ E0.24±0.01. The full spectral energy distribution is well-fitted by synchrotron self-Compton emission from cooling electrons injected with a Maxwellian distribution of characteristic energy γ_b. Fluctuations in the injected power with P_inj∝ γ_b4 explain the observed variability. Conclusions: .The spectral saturation and the power-law dependence of the fractional variability are novel results that may extend to other TeV blazars. The ability of Maxwellian injections to reproduce the observed features suggest second-order Fermi acceleration or magnetic reconnection may play the dominant role in particle acceleration.

Dates et versions

hal-00398299 , version 1 (24-06-2009)

Identifiants

Citer

B. Giebels, G. Dubus, B. Khélifi. Unveiling the X-ray/TeV engine in Mkn 421. Astronomy and Astrophysics - A&A, 2007, 462, pp.29. ⟨10.1051/0004-6361:20066134⟩. ⟨hal-00398299⟩
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